When in sewing together webs of, for example, textile fabrics by a sewing machine, it is sometimes experienced that the webs being intermittently fed underneath the presser foot member of the sewing machine are caused to slip on each other. The slip between the webs being sewn together usually results from the resistance imparted to the lower one of the webs by the feed dog member which is being driven for square motions underneath the webs and onto which the webs are pressed by the presser foot member. The slip thus caused between the webs being sewn together tends to produce crimps in the webs and destroy or at least impair the external appearance of the sewn product. Prevention of the slip between the webs being sewn together on a sewing machine has therefore been a matter of serious concern to users, especially unexperienced users, of sewing machines. The present invention contemplates provision of a presser foot assembly of a sewing machine which will enable even an unexperienced user of a sewing machine to sew webs without causing a slip between the webs.